The developmental restrictions of the cells of the eye-antenna imaginal disc in Drosophila will be studied by clonal analysis using genetic cell markers. Two homeiotic mutants, opthalmoptera and Antennapedia, will be used to study the dynamics of the transformation and the mechanism of structure duplications which accompany both transformations. Some parameters of cellular behavior in the transformed tissue will be measured by clonal analysis. The cellular properties of cells with abnormal amounts of the rDNA cistrons will be investigated through a combination of techniques of somatic cell genetics and cytochemistry.